Multi-range electrical test instrument



Oct. 21, 1958 R. R. SIMPSON 2,857,570

MULTI-RANGE ELECTRICAL TEST INSTRUMENT Filed March 6, 1956 I 2 Sheets-Sheet 1 INVENTOR. v

KAY E. SIMPSON HTTK Oct. 21, 1958 R. R. SIMPSON 2,857,570

MULTP-RA NGE ELECTRICAL TEST INSTRUMENT Filed March 6, 1956 I 2 Sheets-Sheet 2 INVENTOR. R07 E. SIMPSON H6 5 WW United StatesPateht The present inventionrelatesto combination test leads and selector knob for multi-range meters, and is particularly concerned with multi-range meters of the type havinga rotary switch-andte'st leads which are to be selectivelyconnected to; different circuits of the multirange meter. L I

One of theobjects of theinvention is the provision of; an improved multi-range meter structure having a rotary switch which is substantially flush with the housing of the meter, so thatthe rotary switch has no protruding parts that .canbe damaged. Y

Another object of the, invention isithe provision of an improved multi-range .meter ,havinga rotary switch, the face of whichis substantiallyLflush with the housing so that it can only be actuated; by applying the test leads which terminate ina-selector knob carrying connector prongs insertable in the plug which is the movable part of the rotary switch.

Another objectof the invention is the provision of improved combination test leads and selector switch actuator knob in which the connectors carried by the knob are so arranged that theycannonbe inserted except in the part of the rotary switch for which they are intended.

Another object of the invention is the provision of improved test leads and rotary switch structures which are simpler than the devices of prior art, it may be manufactured more cheaply, which have fewer parts and which can only be used in combination, one with the other.

Another object of the invention is the provision of improved test lead and switch arrangements for multirange meters which are so constructed that the test leads must be inserted in the proper holes or sockets to assure the proper polarity of the meter in the circuit and the provision of improved arrangements for accomplishing this result with prongs of different size and or prongs of the same size and alignment lug and socket.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings, in which similar characters of reference indicate similar parts throughout the several views.

Referring to the drawings of Fig. l, which is a view in perspective of the combination test leads and selector with the .multi-range meter prior to assembly.

Fig. 2 is a sectional view showing the selector knob assembly with the multi-range meter.

Fig. 3 is a fragmentary sectional view of one form of rotary switch arrangement, taken on the line 3-3 of Fig. 2, looking in the direction of the arrows;

Fig. 4 is a fragmentary view in perspective of a modification in which a large prong and a small prong are employed to assure proper connections between the switch and leads;

Fig. 5 is another fragmentary view in perspective, showing the arrangement of the parts when the prongs are on the switch and the prong sockets are on the switch handle.

Referring to Figs/1 and 2, indicates a multi -range meterenclosed in an insulating housing 11 provided with a'window 12 for exposing 'thepo'inter -B and scale 14.

The multi-range meter may be of the-typefcovered by prior Patent No. 2,5 09,415 having a plurality of scales and a plurality of positions for ajrQtary sWitch-TS "of the type'described in Patent No. 2,447,718 issuedto Ray R. Simpson, August 24, 1948-.

The rotary switch 15 may consist of 'a cylindr ical' insulating body 16jwhic'h is pr'ovided with a radial; flange 17 adapted to be received in arecess '18 V. in the panelist, surrounding a cylindrical" openiij 20 The rotary switch body 16 may have a bores 21, x

22, each of whichha's therein aapair"ofIesilient contactS 23, 24 for reception of conducting'prongs; l r

The switch body 16 may be rotatablymbimtedinthe bore 20 where it is secured by afpair 'of lock nuts 24, 25-mounted onthe"threaded'portion 26 of'the body leaving suflicient clearance for rotation of "the body 16.

A plurality of switch units 27, 28 may, have their bodies assembled on a' pair'of'scre'wfb olts 29 and may have fixed contacts 30, 31'for engagement "with a' pair' of rotors 32, 33that' areke yedtothe'body 16 to rotate.

with it, carrying movable'contacts 34, 35 thatflcontrol the connection of the test leads, further'to be described,

to the various rangesofthe meter.

The combined test leads and selector knohjare indicated in their entirety at 3,6, includingia pair of flexible multi- Wire conductors 37,38 each of which has a flexible rubber or'plasticinsulating covering."

At one end the insulating .Wires 37,3

inserted into the ,rigid insulating sleevesj39, 40; whic' ,the-

rigid metal connector prong 41,, 42 toQw ductors are connected by. soldering. j

At the other end the -insulating 1ccii tluctors 37i. 38v x n {into he t ed'f nnel i4$ ,4, r ed i t e selector knob45 imdtermihating atthe rigid' metal' connector prong 46, 47.

The connector prongs 46, 47 may have rigid anchoring members 48, 49 held in complementary grooves in the two halves 50, 51 of the selector knob 45, where the prongs are anchored and electrically connected to the conductors 37, 38.

The two halves 50, 51 are held'in alignment by the anchoring formations 48, 49 and a single threaded screw bolt 52 passing through one half and threaded into the otherhalf of the selector knob or provided with an embedded nut.

The operation of the assembly is as follows:

The rotary switch body 16 being flush with the front of the housing 11, it has no projecting parts by means of which it may be rotated. It is adapted to receive the prongs 46, 47 which are connected to the test leads and mounted in the selector knob.

The selector knob has a knife edge at 53 which serves as a pointer for registry with the indicia on the scale 54 of the switch 15 when the prongs 46, 47 are inserted in the apertures 21, 22 engaging the resilient contacts 23, 24.

The selector knob is adapted to be assembled with the switch. The switch may be turned to the proper switch body 15 to make it necessary that the prongs shall be inserted in the proper apertures so that the meter will read forwardly on its scale.

Referring to Fig. 4, this is a modification in which 2,857 570 5 lfg tentediget; "1958 would V e impossible to so; connect would havethe'wrong po1arity,'such as,to causesa backward readingionthe meterf I Referringto .Eig. -5, ;th.isfis: a view similarto ,Fig. 1

of,a-:;modification in which the switch member; is provided with one large prong 69 and:one--small prong for cooperation with v a, selector knob 71;, having -,one large socket'fiziffor receiving large prong 69- and one-:small.

socket. 7,3 for receiving small-5 prong .70.

It should also be understoodithat, when knob 5,3,; is provided theoifzcenter lug 60, itmay also beiconstructed ,asingl .prolig,.-inthe:.event a 6.0m:- mon connection v p roriide d elsewhere, and only one Pm gS IQQHiIF The switchv cannot; be actuatje idz except using proper test leadshaving connection prongetmounted on. a, selector knob. The .user is thus assured that the. meter -will be employed with low resistancetestfileads which are properlyinsulated forlsafety and-adapted to be 'usedfor high accuracy electrical measurements.

whilell meantimea I invention, many modificationsg may be made without departing 'fromthe-spiritof the invention, and I donot wish tobe limited to the'p recise details 10f construction set forth, :but desire to. avail myself ofi changeswithin the-scope ofjthefappendedclaims.

, Having thus described invention, which I claim as 'new and desire to secure Letters-Patent :of the Unite.d;States, is:

l 1, Afnniltipleerange'eleetricaljtest instrument: commie:

mg, in combination, a housing havinga panel, said panel being provided with acir'cular aperture, a meter mounted:

in said housing, .a switchhody fixedly mounted on the inner; side, (of, said gpanel surrounding said aperture, said switchbo'dyhaving a of fixed contacts arranged the -leads that 1 they i thegselector:

preferred embodiment of in' at least onecirciilaibank, a"' switch rotor rotatably I mounted on said panel within s idnapcrtnre QQQKiA J,

contacts.

of said switch body, said switch rotor having a front face substantially flush with the front face of said panel, 1 and carrying at least one radially-extending arm posi-' tioned for cooperative switching action with said fixed contacts, said switch rotorzalsqghaving in its frontface a pair of openings and a pair of female electric contacts, mounted on its rearside-directlybehind-said openingsa male connector plug adapted tomate .withnthe front v' faceof said switchrotor andhavingayair; ofgmale contact prongs fixedly spaced to enter said opcningszaudito make electrical connection with said female contacts, and a pair of insulated testleads havingtest' prods at one end,

the other end of said; painof test leadstbeing secured within said male connector plug and being respectively connected to said prongs, said male plug being formed to provide convenient manual means for rotating said switch rotor? whe'n- -sa-itl' ='prongs are inserted -within said female 2.. A'multiplearange electrical test instrumentaccording to claim 1 wherein= one ofsaild prongs -and oneof said" v openings is' larger in' cross -seetion than the other of said prongs and said openings.

3. muttiple' range electrical test instrument accord ing toclaim -1- wherein one of said prongsand one of-saidf openings are respectively differently shaped-than the otheh oflsaidprongs and the other-of said' openings,'-whereby* said prongs may be inserted inasa'id openings win-only; a .single'melative position i r g 4. A .multiple range electrical test instrument acc'o rd ing to claimv 1 I having additional means on said malef plug and sa'rct switch 'rotorperrnitting said "plug and rotor A to 1 mate atogether in only one relative position.

' References Cited in the file ofethis ypatent .unrr'nnsrarns mews r 1,669,666 May,1-5','192 s anti ar-s :au 

